Centimeter-scale fullerene-free tin-based perovskite solar cells achieving over 14% efficiency

Fullerene-based materials have traditionally served as the primary electron transport layers (ETLs) in environmentally friendly tin-based perovskite solar cells (TPSCs) due to their suitable band structures. However, they suffer from limitations such as high cost, complex synthetic process, low electron mobilities, limited interactions with Sn-based perovskites, and challenges in tuning their chemical and electrical structures, which have hindered further improvements in power conversion efficiency (PCE) of TPSCs. To tackle these issues, we propose a fullerene-free TPSC architecture and introduce a series of low-cost non-fullerene materials, i.e. fluorinated triple-acceptor polymers (named as P1 , P2 , and P3 ), as alternative ETLs. Compared to fullerene-based ETL, such as indene-C ₆₀ bisadduct (ICBA), these non-fullerene ETLs exhibit facile synthetic process, three orders of magnitude higher electron mobilities, and high structural flexibility. Additionally, these non-fullerene ETLs form continuous and conformal interfaces with Sn-based perovskite layers, enabling stronger and more uniform interactions over large-area Sn-based perovskite layers. In 1-cm ² TPSCs, particularly those using the P3 ETL, we achieve a remarkable PCE of 14.39%, surpassing the PCE of 10.61% observed in 1-cm ² TPSCs with the ICBA ETL. Notably, TPSCs with the P3 ETL achieved a record PCE of 16.06% for small area of 0.04-cm ² (certified at 15.90%). Furthermore, the fullerene-free TPSC with the P3 ETL demonstrates exceptional stability, showing no significant degradation over 1200 hours of shelf storage and maintaining nearly 86% of its initial PCE after 550 h of maximum power point tracking under continuous 1-sun illumination. This enhanced stability is attributed to the robust hydrophobicity conferred by the long alkyl side chains. Overall, this study substantiates the substantial potential of fullerene-free TPSCs using non-fullerene ETLs in advancing both the photovoltaic performance and stability of large-area TPSCs.